/*
 * Copyright (c) The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

import { TokenStream } from "../TokenStream.js";
import { ATNConfigSet } from "./ATNConfigSet.js";

/**
 * This is the base class for gathering detailed information about prediction
 * events which occur during parsing.
 *
 * Note that we could record the parser call stack at the time this event
 * occurred but in the presence of left recursive rules, the stack is kind of
 * meaningless. It's better to look at the individual configurations for their
 * individual stacks. Of course that is a {@link PredictionContext} object
 * not a parse tree node and so it does not have information about the extent
 * (start...stop) of the various subtrees. Examining the stack tops of all
 * configurations provide the return states for the rule invocations.
 * From there you can get the enclosing rule.
 */
export interface DecisionEventInfo {
    /**
     * The invoked decision number which this event is related to.
     *
     * @see ATN#decisionToState
     */
    decision: number;

    /**
     * The configuration set containing additional information relevant to the
     * prediction state when the current event occurred, or `null` if no
     * additional information is relevant or available.
     */
    configs: ATNConfigSet | null;

    /**
     * The input token stream which is being parsed.
     */
    input: TokenStream;

    /**
     * The token index in the input stream at which the current prediction was
     * originally invoked.
     */
    startIndex: number;

    /**
     * The token index in the input stream at which the current event occurred.
     */
    stopIndex: number;

    /**
     * `true` if the current event occurred during LL prediction;
     * otherwise, `false` if the input occurred during SLL prediction.
     */
    fullCtx: boolean;
}
